In 2154, after T'Pol returned to Vulcan following the Xindi incident, her mother, T'Les, urged her to marry Koss, but she still refused. Koss visited T'Pol and attempted to persuade her to marry him by offering to let her resume her career if she spent one year with him on Vulcan. He also offered to help her mother regain her position at the Vulcan Science Academy, from which T'Les had been dismissed because T'Pol had been involved in an incident at P'Jem. Under the condition of remaining on Enterprise for the time being, T'Pol finally agreed to Koss' proposal, and the two were subsequently married at T'Les' house. (ENT: "Home")

In the writers' second draft script of "Breaking the Ice", this character's name was consistently spelt "Kos". In an ultimately discarded line of dialogue from the same script, T'Pol specified that Koss had been betrothed to her since they were fourteen years old.

In the script for "Home", Koss was initially described as "a striking Vulcan man approximately T'Pol's age." This would put his year of birth around 2088. After providing his name, the script went on to say, "Although tall and severe in appearance, we sense a total lack of pretension in this Vulcan."